On Wednesday 04 July 2007, Rodolfo Giometti wrote:
> Hello,
>
> Looking at other rtc drivers I noticed that during the release()
> method we should disable IRQs as follow:
>
> static void ds1307_release(struct device *dev)
> {
> struct ds1307 *ds1307 = dev_get_drvdata(dev);
>
> if (ds1307->irq >= 0) {
> ds1307->irqen = 0;
> ds1307_update_alarm(ds1307);
> }
> }
On the RTC list, the outcome of that discussion was that
the release() method -- not generally implemented at this
time, and only supporting the /dev/rtcN access mode -- should
only disable the IRQs enabled through that /dev/rtcN file.
Now, it turns out that of the three kinds of RTC IRQ (alarm,
once-per-second, and 2^N-per-second), two of those modes can
be accessed through in-kernel APIs outside /dev/rtcN calls:
- 2^N-per-second "periodic" irqs, using rtc_irq_set_freq()
and rtc_irq_set_state()
- alarm irqs, using rtc_set_alarm()
So it would be incorrect to disable those IRQs, when some
other kernel activity had enabled them. But for now it
would be correct to always disable once-per-second "update"
IRQs in a release() method.
There's a separate issue -- longstanding, not new to the
RTC framework -- of how several consumers of RTC IRQs ought
to share the different kinds of IRQ.
> But if I wish using RTC IRQ line to turn also the board ON, not just
> to put to sleep it, I should leave the IRQ line on!
That can be done with /sys/class/rtcN/device/power/wakealarm,
writing it to the time (in seconds) the RTC alarm should kick
the board's power-on circuitry.
- Dave
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